The insulation of high voltage power cables will degrade after a period of time. One remediation process for the insulation of medium and high voltage power cables requires the injection of a remediation fluid into the free spaces of a cable. In many instances, the injection process takes place while the cables are energized. When the remediation process is performed on energized cables, special injection terminations (injection “elbows”) may be used. Injection terminations are similar to industry standard cable terminations except that they have a special access port designed to allow for the injection of fluid into the cable. The fluid is commonly injected into underground cables from a fluid feed line, which is connected to a fluid feed tank.
One remediation process for the insulation of medium and high voltage power cables requires the injection of a remediation fluid into the free spaces of a cable's conductor. In many instances, the injection process takes place while the cables are energized. When the remediation process is performed on energized cables, a class of special injection terminations may be used. Injection terminations are similar to industry standard cable terminations except that they are sealed to the environment and have special access ports designed to allow for the injection of fluid into the cable.
The fluid is commonly injected into underground cables from a fluid feed line, which is connected to a fluid feed tank, at the injection termination. When fluid is injected into the cables at the injection port of the injection terminations, it is assumed that the fluid flow is only in one direction, flowing from the feed tank to the cable. However, as the cable fills and the fluid system begins to stabilize, temperature changes that occur inside the cable or outside in the environment around the feed tank can cause the pressure of the system to fluctuate. The pressure fluctuations can lead to instances where the pressure inside of the injection elbow is greater than the pressure inside of the fluid feed tank. At this point, fluid flow would reverse, moving from the injection elbow back into the fluid feed tank.
The fluid that travels in the reverse direction, out of the injection elbow, carries contaminants from the cable to the feed tank. These contaminants can be conductive or semi-conductive, effectively reducing the insulating value of the remediation fluid in the fluid feed line that separates the energized cable from the feed tank and a conductive pathway can be formed.
Therefore, there exists a need to prevent back flow of contaminated fluid from the injection elbow to the fluid feed tank.